How to find image usage? Outliner / Data API / Images
These are possibly two different questions :).


To unpack an image, go to Image Editor and click the Unpack icon.
To remove unused images, select all and RMB > Clear Fake User.
All unused images will be removed after reopening your .blend file.
Only images that are currently in use will stay in the .blend file.


Unpacking a file  



Removing images not in use